A Liberal Carrier Sensing for Increased Spatial Reuse in Multi-Hop Wireless Ad Hoc Networks

Recent experimental results have shown that the minimum signal-to-interference ratio required at a receiver (CP_th) depends on the order of arrival of the overlapping frames. For a given sender-receiver distance, this differential capture capability of a receiver leads to two distinct interference ranges (r_i) around the receiver, and its value is much smaller when the sender´s frame arrives earlier. This feature also suggests a possibility of increased spatial reuse by allowing the (secondary) nodes outside the primary receiver´s r_i to communicate concurrently once the primary receiver starts its DATA reception. In this paper, we propose a liberal carrier sensing (LCS) scheme wherein some already available information at an otherwise ´exposed´ receiver are exploited to help decide when it is safe to respond to a secondary transmission request. The proposed modification in the carrier sensing approach results in a significantly improved spatial reuse, thereby increasing overall system throughput. Our simulation studies show that, compared to the conventional carrier sensing scheme with differential capture capable receivers, the end-to-end TCP throughput with LCS can be improved by more than 20% in regular topologies and up to about 9% in random topologies.